Genetic testing is recommended for women and girls who are at risk of being hemophilia carriers, but a 2025 study conducted at one hemophilia treatment center (HTC) suggests that most girls at risk aren’t getting tested.
The study, by researchers at Seattle Children’s Hospital, looked at 64 girls under 18 who were at risk of being carriers because they had a brother with hemophilia. The researchers found that only 17 of the girls (27%) had received genetic testing prior to receiving genetic counseling at the HTC.
Conducting genetic testing on girls is the best way to determine if they are a carrier for hemophilia. Some carriers have bleeding symptoms, and this is not easy to predict with a factor level alone. In addition, about 50% of carriers can have factor levels below normal, meaning they have a diagnosis of hemophilia themselves.
“Being a carrier means you could have abnormal bleeding, and the only way to make that carrier diagnosis is with genetic testing, so that’s one of the best arguments to go ahead and have it done,” says study co-author Kristin Maher, M.D., Ph.D., a hematologist at Seattle Children’s Cancer and Blood Disorders Center.
A female carrier with mild hemophilia should be treated just like a male with mild hemophilia, Maher says, “meaning they should have emergency factor on hand at home, and they should be treated prior to surgery.”
In addition, hemophilia carriers often require treatment for heavy menstrual periods, as well as iron deficiency and anemia.
Common Barriers to Genetic Testing
According to Maher, there are several barriers to genetic testing for girls who are at risk of being hemophilia carriers:
Insurance Problems
Genetic testing usually requires prior authorization from an insurance company, and sometimes coverage is denied. Maher says that’s usually due to the persistent misconception that hemophilia carriers can never have symptoms themselves.
“Oftentimes, the reason that genetic testing for a young girl will be denied is that the test result is thought to only be needed for reproductive care, which implies that the only purpose of the testing is to identify whether a male child could be at risk,” Maher says.
Lack of a Known Genetic Variant
The gold standard for carrier testing is to do targeted testing for a known family variant. With hemophilia A, for instance, instead of looking for a variant in the entire factor VIII gene, clinicians do targeted testing for the variant that the family member has.
“This means we need to have a family member who has had genetic testing and whose results we have access to,” Maher says. In the study, there were several girls who weren’t eligible for genetic testing because the researchers didn’t have access to a family member’s genetic variant.
Family Reluctance
Maher says some parents decline to have their daughters tested because they’re concerned that a genetic test result may affect their child’s ability to obtain insurance later in life. Others decide to wait until their daughter is 18 and can make the decision herself.
“There are potential benefits and potential downsides to genetic testing, and that’s why genetic counseling is so important,” Maher says. “Genetic testing is a choice, but it should be offered with all of that information.”
Learn more about what women and girls should know about getting tested for bleeding symptoms.